Will a 40 Channel Switch From an AM CB...

Yeti Communications Ltd said:

hi
yes it can be done HOWEVER ..
40 channel am plla02a switches come in two flavors either N224>N286 (ch1>ch40 dont worry about the inverted codes in this example ) or N330>N286 (ch1>ch40) depending on chassis it came from...

now heres the bite
ssb pll02a radios use N255>N211(ch1>ch40) so as you can see the Ncode or binary weighting presented to the pll would put the radio on a different frequency to what you intend
Ah OK, I thought there might be a catch.
5 ways around this
either replace the mixer crystal in the radio(after replacing with a pll02a am switch to correct the frequency of the radio in other words shift it back to the correct fcc band (expensive in this day and age)
or
put a binary adder in between the new channel switch and the pll to correct the binary weighting (4008) (20 bucks with a board and some resistors)
or use a pic ic programmed to correct the binary weighting ..both of those options will allow more bands to be added (about 20 bucks)
or old school way a eeprom with code to correct binary weighting
by correct binry weighting i mean convert say 330>286from switch in to 255>211 that the pll needs to be on correct ch1>ch40

as you can see its not "simple"
switches from other radios with differnt plls will be the same issue

i have done may hybrids swaps to radios that you cant get 40 channel switches for converting from 18/23 channel to 40 but always you need to use one of the above methods to correct either the frequency or the code presented to the pll to get back on the band required
Thanks for all that info, Mike! That's a lot of food for thought, and educational as well.

of course the "simple" way is just throw a digimax in it but i guess your intention is stock 40 channels which i am sure you are well aware of ..ray at razor radio can do the install and hes playing with a pllo2a to mc145106 conversion at moment if you really want more channels
This is interesting, I hadn't heard of this guy, thanks. I was thinking about a Digimax, but looking at the install in a GE B model, that is on You Tube () kind of puts me off, all that mess of wires and the drilling and cutting.

end of day just buy a wrecked ssb chassis (plloa2) from usa where 40 channel switches are common
I have been looking, not many around, only the odd AMer, hence my question. I would also be worried that the switch is worn to death.[/QUOTE]

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nomadradio said:

The PLL02A can accept about 250 input codes, dividing the chip's input frequency by a divisor of about 5 to 255.

The radio only needs 40 of them.

Which 40 out of 250 possible?

Depends on the designer's choice of the internal frequencies used by the radio.

The most-efficient choice of internal frequencies for SSB models is not the same as for an AM-only radio.

As a result, the AM and SSB radio will each use a different 40 out of those 250 possible binary codes. Same chip, different selector, different sequence of binary numbers coming out of it.

The exact combination of ones and zeroes that come out of the channel selector is what sets the PLL's internal frequency, the one it locks on to for each channel.

This sequence of one and zero may count upwards, with a smaller binary number on channel 1 and a higher number on channel 40.

For reasons we'll just skip for now, the binary sequence may instead count DOWN from channel 1 to channel 40. Both AM and SSB radios have been sold with this internal feature. On channel 1 the selector feeds the highest number into the PLL chip, and on channel 40, this number is smallest.

Folks who characterize what's different from one selector to the next will use a decimal equivalent to the binary input to the chip when it's set to channel 1, and for channel 40. This is what they mean by "91 to 135" or "78 to 122". Much easier than trying to remember the pattern of the binary on and off bits.

73

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